Vapor deposition process and device



June 8, 1965 AUXILLIA RY GAS R. BAKISH ETAL VAPOR DEPOSITION PROCESS AND DEVICE Filed March 16, 1961 PLAT IN ZONE POWER SUPPLY AND CONTROL United States Patent O VAPR DEPOSITIGN PRGCESS AND DEVICE Robert Bakish, Brighton, Donald B. Irish, Newtonville,

and Iwan Marinow, Allston, Mass., assignors to The Alloyd Corporation, Cambridge, Mass., a corporation of Massachusetts i Filed Mar. 16, 1961, Ser. No. 96,124 1 Claim. (Cl. 117-1071) The present invention relates to the deposition of a metal from a decomposable metal bearing vapor continuously onto a iilament and, more particularly, to a process and a device for achieving such deposition. It is often desired to coat the surface of a strand of particular composition with a particular metal in order to impart predetermined physical, chemical and mechanical characteristics. Thus, for example, it may be desired to coat glass or quartz strand with a refractory or other metal in order to prevent surface fracture and chemical contamination tending to greatly reduce the tensile strength of the strand. It has been proposed to coat such a strand by depositing a metal from a metal bearing vapor at a temperature at which the vapor is unstable. It has been customary to perform such a process at reduced pressure, and/ or under hermetic conditions whereby the cost of vacuum equipment has been an important economic consideration in the commercial feasibility of such a process.

The primary object of the present invention is to provide processes and devices for coating the surface of a strand moving continuously in a given direction by deposition from a metal bearing vapor in an auxiliary gas at a total pressure which is at least approximately normal atmospheric in order to avoid hermetically sealing the system from its exterior. The system involves moving the filament and an Yauxiliary gas through a path including a preheating zone in which the auxiliary gas is heated, a vaporizing zone in which the auxiliary gas and the metal bearing gas are mixed and a plating zone in which the filament is heated and the metal bearing vapor is decomposed in order to deposit the metal on the filament. Preferably, the auxiliary gas is introduced through the preheating zone and the filament is introduced through the plating zone. A slightly and continuously decreasing pressure gradient is maintained from the preheating zone to the plating zone in order to prevent the entry of metal bearing vapor into the preheating zone. A simple manifold communicating with both the plating zone and the exterior exhausts the residual gaseous mixture from the plating zone.

Other objects of the present invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the apparatus possessing the construction, combination of elements and arrangement of parts, which are exemplied in the following detailed disclosure, and the scope of which will be indicated in the appended claim.

For a fuller understanding of the nature and objects of the present invention, reference should be had to the following detailed description taken in connection With the accompanying drawing wherein there is shown a diagrammatic, fragmentary view of an apparatus for effecting a specific process of the present invention.

The specific process illustrated in the drawing involves the steps of advancing a strand to be coated and an auxiliary gas in opposite directions through an elongated, substantiallytubular, path comprising, in sequence in the direction of auxiliary gas ow: an entrance aperture that is relatively small in diameter; a preheating zone that heats the auxiliary gas to an initial temperature and receives the auxiliary gas from a suitable supply; a mixing zone in which the auxiliary gas is owed into contact with a metal bearing compound that is thereby volatilized; a plating zone within which deposition of the metal from the metal bearing vapor occurs; and through a second aperture of relatively large diameter, which in addition to permitting advancement of the filament into the plate zone conducts the auxiliary gas and residual metal bearing Vvapor from the plating zone to an exhaust. In this system Vthe metal bearing compound is an organometallic, a metal hydride, a metal carbonyl or a metal halide, combinations thereof and mixtures thereof. It is known that useful rates of metal deposition from such gaseous metal bearing compounds occur generally within the range from to l000 C. The auxiliary gas may be reactive material such as hydrogen or carbon monoxide or an inert material such as argon (or other noble gas) or nitrogen. The total pressure within the path ranges approximately from 14 to 30 p.s.i., there being a slightly and continuously decreasing pressure gradient from the iirst aperture tothe second aperture by virtue of the relatively small diameter of the first aperture and the relatively large diameter of the second aperture. In order to secure a satisfactory bond between the metal coat and the surface to which it is applied, it is desirable that the coat be composed of a substantially pure metal, either elemental or alloyed, it being particularly important that the metal be substantially oxygen free. The filament, for example, may be composed of a vitreous compound such as glass,

in conventional fashion, containing silicon dioxide fusedV with such materials as alkali oxides and alkaline earth oxides. The present invention, in its broadest aspects, also contemplates that the filament be composed of ai material, other than a vitreous material, such as a refractory metal. Preferably the metal bearing gas and the auxiliary gas range in proportion, by total weight, from 1 to 30% metal bearing gas and from 99 to 70% auxiliary gas. Y

The gaseous metal bearing compounds preferably are selected from: carbonyls'such as ferrie carbonyl, molybdenum carbonyl, nickel carbonyl, chromium carbonyl, tungsten carbonyl and cobalt carbonyl; halides such as chromium chloride, tungsten chloride, molybdenum chloride, aluminum chloride, aluminum bromide, aluminum iodide, cobalt bromide, cobalt chloride, fefiic chloride, germanium bromide, germanium chloride, manganese fluoride, chromium fluoride, nickel bromide, nickel chloride, tin bromide, tin chloride, tin fluoride and titanium chloride; alkyls such as aluminum diisobutyl, aluminum triisobutyl, aluminum triethyl and molybdenum ditoluene; aryls such as chromium dibenzene, molybdenum dibenzene, vanadium dibenzene and vanadium dii-mesitylene di-iodide; olefins such as bis-cyclopentadienyls of iron, manganese, cobalt, nickel, rhodium and vanadium; esters such as cupric acetylacetonate, manganic acetylacetonate, titanyl acetylacetonate, platinum acetylacetonate, nickel acetylacetonate, dibutyl tin diforma-te, copper formate and copper acetate; nitro compounds such as copper nitrosyl and cobalt nitrosyl, carbonyl hydrides such as antimony hydride, copper hydride, aluminum hydride, and tin hydride;Y

and combinations and mixtures thereof such as alkyl and aryl carbonyls including benzene chromium tricarbonyl, p ihenanthrene chromium tricarbonyl, o-xylene chromium tricarbonyl, naphthalene chromium tricarbonyl, benzene molybdenum tricarbonyl, cyclo-octadiene molybdenum tricarbonyl; bis-cyclopentadienyl chlorides, bromides and iodides of titanium, zirconium, hafnium, vanadium, molybdenum, tungsten and tantalum; cyclopentadienyl carbonyls such as cyclopentadienyl manganese tricarbonyl,

bis-cyclopentadienyl carbonyls of molybdenum, tungsten or iron; carbonyl halogens such as sodium carbonyl bromide, ruthenium carbonyl chloride; and organo hydride compounds such as aluminum dimethyl hydride.

The drawing illustrates diagrammatically apparatus for coating a tilament in accordance with the present invention. This apparatus comprises a tube 10, a tank 26 and a tube 36 as follows. Tube 10 provides a preheating zone from which a filament 12 is advanced to a takeup 13 through a suitable aperture 14 and into which a suitable auxiliary gas 16 is introduced through a valve 13, a liow meter 20 and an entrance conduit 22. Tank 26, which detines a mixing zone 24, is provided with a pair of end covers 28 and 30 having apertures therethrough for the entrance and exit of gas and iilament movement and contains a suitable open top vessel 32 Within which a metal bearing compound 34 is carried. Tube 36 defines a plating zone that receives the auxiliary gas and metal bearing vapor mixture from tank 26. The gaseous mixture leaves tube 36 through a suitable aperture 38 in such a way that it is exhausted by a manifold 40. Filament 12 enters tube 36 through aperture 38 from supply spool 41. Tube is provided with a heating unit 42, which includes a coil enveloping tube l0, an insulating cover-ing and a control 44. Tank 26 includes a coil enveloping the tank, an insulating covering and a control 46. Tube 36 includes a coil enveloping tube 36, an insulating covering and a control 50. Tube 10, tank 2d and tube 36 are suitably mounted as at 52, 54 and 56 on a suitable base 58. A suitable normally capped conduit 60 is provided above vessel 32 through tank 26 for the purpose of permitting the introduction of additional metal bearing compound 34. As indicated above, aperture 14 is of smaller diameter than aperture 33 to ensure that the pressure decreases along the path from aperture 14 to aperture 38. The rate of plating in tube 35 is controlled by adjusting controls 44, 46, 50, and 61. The rate of advancement of filament I2 is determined by a speed control 61 which drives guide rollers 57 at opposite extremities of the path through which iilament l2. is advanced.

The following non-limiting examples will further illustrate the present invention:

Example I In one specific example of the foregoing process atleeted by the above described apparatus, a liber glass filament (or strand of iilaments) is advanced from supply spool 41 into tube 36. Nitrogen is introduced into preheating zone 10 whereit is heated to approximately 90 C. The flow of heated nitrogen into the mixing chamber picks up vapor` of molybdenum carbonyl in vessel 32. The pzttial pressure of the nitrogen is approximately five times the partial pressure of the molybdenum carbonyl. The total pressure is approximately atmospheric. The plating zone is heated to a temperature of approximately 350 C. The ow rate through the system is approximately 1.0 cubic foot perV hour. The rate of advancement of the filament is approximately ft./min. Each increment of glass lilament as a result is coated with a molybdenum layer approximately .0005 inch thick.

Example 1I The foregoing process is repeated except that the auxiliary gas is nitrogen and the metal bearing gas is chromium dicumene.

Example Ill The process of Example I is repeated except that the auxiliary gas is nitrogen and the metal bearing gas is iron dodecacarbonyl, the nitrogen being initially at room ternperature and the iron dodecacarbonyl being at a temperature of 135 C. Excellent p results.

ating on the glass filaments Example 1V Example V Example I is repeated except that the auxiliary gas is argon and the metal bearing gas is cyclo-octadiene molybdenum tricarbonyl, both at a temperature of approximately 110 C.

Example VI The process of Example I is repeated except that the auxiliary gas is hydrogen and the metal bearing gas is copper acetylacetonate, both at a temperature of approximately 300 C.

Example VII The process of Example I vis repeated except that the auxiliary gas is hydrogen and the 4metal bearing gas is aluminum hydride, both at a temperature of C.

Since certain changes may be made in the above process and apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted in an illustrative and not in a limiting sense.

What is claimed is:

The process of continuously metal plating a filament, said process comprising the steps of electing movement of said lilament through a continuous path, said movement in sequence being through an aperture of relatively large cross section, an elongated plating zone, a mixing zone, an elongated preheating zone and an aperture of relatively small cross section, the yinner extremities of the elongated zones communicating with opposite extremities of said mixing zone, and the larger and smaller apertures communicating with the outer extremities of said elongated zones, introducing an auxiliary gas into said preheating zone at a point adjacent to said smaller diameter aperture, heating said auxiliary gas in said preheating zone, flowing said heated auxiliary gas in contact with a heat decomposible metal bearing compound in said mixing zone to generate a metal bearing vapor mixture, flowing said metal bearing vapor mixture into said plating zone, heating said metal bearing vapor mixture at said lament in said plating zone, thereby decomposing said metal bearing vapor and depositing said metal on said tilament, exhausting the residue of said metal bearing vapor mixture substantially exclusively through said larger diameter aperture from said kcontinuous path, said larger and smaller diameter apetures establishing a decreasing pressure gradient from said smaller diameter aperture to said larger diameter aperture, the temperature of said plating zone ranging from 100 to 1000 C., the pressure within said path ranging approximately from 30 to 14 pounds per square inch, said metal bearing vapor and said auxiliary gas ranging in proportion, by total weight from l to 30% metal bearing gas and from 99 to 70% auxiliary gas.

References Cited by the Examiner UNITED STATES PATENTS 2,749,255 6/56 Nack et al. 117-107 2,759,848 8/56 Sullivan l17-l07.l 2,986,115 5/61 Toulmin 117-107 RICHARD D. NEVIUS, Primary Examiner. 

